Positive social relationships have consistently been associated with better health, although the neurobiological underpinnings of these observed effects are not well understood. Valuable insight may be gained by a life course perspective as it is becoming increasingly apparent that early life social experiences are crucially related to later life functioning and well-being. The overall goal of the proposed work is to explore novel biological pathways that help to explain how social relationships influence health. Recent theorizing on the biology relating positive social and emotional factors to health and patterns of resilience suggest that the oxytocin system may underlie some of the observed beneficial effects. Historically, most work on the oxytocin system in humans has been tied to reproductive outcomes (e.g., lactation), with more limited work on children and young adults. A growing body of experimental research with animals suggests that early in life, oxytocin not only creates powerful social bonds between a mother and child but may also stimulate growth and restorative processes as well as buffer deleterious stress-related neuroendocrine activation throughout the life course. Moreover, the animal literature has suggested that oxytocin is more potent in the presence of higher estrogen levels, leading investigators to hypothesize that effects of oxytocin are stronger in women than men, but few studies have tested this hypothesis in humans. A better understanding of the inter-relationships between oxytocin, social relationships, stress, and health will be gained by examining these factors in a controlled laboratory setting. The immediate goal of this research is to determine whether oxytocin plays a critical role in determining neuroendocrine, cardiovascular, and subjective responses to stress across age and gender, and to examine the effects of oxytocin in relation to those of social support. To achieve these goals, experimental research is proposed to examine the effects of exogenously administered (intranasal) oxytocin on psychological and physiological outcomes, under conditions of stress. The specific aims of this exploratory project are to test the following hypotheses: